I haven't seen this error before and can't find anything in the help or knowledgebase.

I uploaded from a customer PLC (L24ER version 30.011) to get the latest info, made my changes offline, then went to download back to the PLC and got the following error:
"Failed to download over port specified by communication path. Cannot disable active communication port. Either select a different communication path or ensure that all active ports remain enabled"
Bottom has Error 457-80044478... which I couldn't find any information on.

I tried clearing and resetting the comms path with no luck. I find it odd that I can connect, save, upload, edit, etc but just can't download. I ended up just making all of my changes online instead so I could get my job done, but for future knowledge I'm wondering why that error appeared.

This machine was originally created in version 20. The customer has upgraded it to version 30.011 since then. Not sure if that would do anything wanted to note it.
My gut tells me it's Win10 related as I've been trying to use it as much as possible to see what works and what doesn't. I have a Win7 partition on my computer as my backup plan so I'm going to download the gigs of 30.011 joy later, install on 7, and try that tomorrow.
Any other suggestions or possible causes?

I recently had the exact same error. I just updated the firmware on an L33ER to v30. I have been using win10 OS for quite a while also. The PLC went from V20 which I was doing downloads on during development every morning to V30 which I now cannot "download to" through Ethernet. The only way I have found to actually download is through the USB port on the PLC. I talked to one of my local Rockwell guys and he sent me here and suggested I utilize my tech connect agreement and call Rockwell. I was hoping to reply here to see what you may have done to resolve this problem?